Whenever travelling around the world, if someone carries a 110 volts hair dryer provided with a plug of two flat pins, which is popularly used in USA, Canada, Japan, and Taiwan, the hair dryer will then be inoperative in Europe or Middle East area wherein a power supply of 220 volts and two or three round holes are provided in a wall socket, because of an impossible electrical connection between the dryer plug and the socket of power supply.
It is therefore expected to invent a universal adapter which can be used worldwide for an electrical connection between a plug of an electric appliance with any power-supply socket around the world.